1. Field of the Invention
This invention relates to an apparatus for operating and transferring a cover for a manhole for operating and inspecting piping, an electric cable, a tank or the like which is laid underground, and more particularly to a manhole cover operating and transferring apparatus which is adapted to efficiently lift a manhole cover provided with any operating hole of the through-hole type including that of the pick-hole type through the operating hole and then transfer it to another place. The present invention is not to carry out the separation of an edge of a manhole cover fixed to a support frame of a manhole due to clogging or the like from the support frame but is directed to a manhole cover operating and transferring apparatus for lifting and transferring a manhole cover of which an edge has been separated from the support frame.
2. Description of the prior Art
Recently, rapid progress in mechanization and laborsaving in civil engineering causes the physical strength of an operator to decline, resulting in the operator being often injured or sustaining an injury of the lumber vertebra such as a ruptured intervertebral disk, for example, during the operation of a manhole cover which requires the operator to exercise force of 50 kg or more. In general, manhole covers are formed with various kinds of operating holes which are adapted to be engaged with a distal end of lifting means such as a lifting lever to lift it.
A manhole cover operating and transporting apparatus was proposed which is constructed to handle a manhole cover formed with a particular operating hole in a laborsaving manner. However, the proposed operating and transporting apparatus is not adapted to be efficiently used for a manhole cover formed with an operating hole of the pick-hole type. Thus, a manhole cover provided with an operating hole of such pick-hole type and generally having a weight of 150-200 kg has been obliged to be operated in a manner such that a distal end of a pick is inserted into the operating hole and the manhole cover is lifted through the other end of the pick with the combined labor of at least two.
Now, an operating hole provided at a manhole cover will be described with reference to FIG. 1. As shown in FIG. 1, various kinds of operating holes are formed at a manhole cover depending upon the type of a manhole cover. In FIG. 1, reference numeral 20 designates a manhole cover and 22a to 22f designate operating holes formed at the manhole cover 20. In general, such operating holes each are typically arranged in the circumferential direction of a manhole cover and in the vicinity of a periphery of the cover. In FIG. 1, a single manhole cover 20 is provided with all kinds of operating holes 22 in a lump for the sake of brevity. It should be noted that normally one or two such types of operating holes are selectively provided at a manhole cover depending upon the type of a manhole cover. Operating holes designated by reference numerals 22a and 22b in FIG. 1 are of the type defined by the British Standards and are typically used in Japan. The operating holes 22a and 22b each are formed to have a central circular portion and a pair of extensions outwardly radially extending in the opposite directions therefrom, so that such a hanging hook as generally indicated by reference numeral 24 in FIG. 1 which is constructed to have projections 26 provided on both sides of a lower end thereof may be engagedly fitted at a lower portion thereof in the operating hole. More particularly, the operating holes 22a and 22b each are operated by means of the hanging hook 24 in a manner such that the hanging hook 24 is inserted through the operating hole 12a or 12b and rotated by an angle of about 90 degrees to securely support a lower side of the manhole cover 10 on the projections 26, and then the hanging hook 14 is upwardly moved to lift the manhole cover.
An operating hole of such type as designated by reference numeral 22c is formed to include a blind hole portion having a round bottom and a rectangular planar shape and a rod portion provided in a manner to be laid across the blind hole portion to separate the surface of the blind hole portion into two sections, so that a hanging hook as generally designated by reference numeral 28 in FIG. 1 may be operated with respect to the manhole cover 20 in a manner such that a hook portion 30 of the hanging hook 28 is engaged with the rod portion of the operating hole 22c to scoop the manhole cover 20 therethrough and then the hanging hook 28 is elevated to lift the manhole cover.
An operating hole designated by reference numeral 22d is of the so-called hatch-type and comprises a blind hole portion and a handle provided in a manner to be retractable with respect to the manhole cover 20. The operating hole 22d is likewise operated by a hanging hook of such type as indicated by reference numeral 28.
Operating holes indicated by reference numerals 22e and 22f in FIG. 1 are of the so-called pick-hole type and comprise through-holes formed into substantially circular and square shapes, respectively. A manhole cover provided with the operating holes 22e or 22f is operated in a manner such that at least two operators cooperate to lift the manhole cover by means of a pick which is inserted at a tip end thereof into the hole. An operating hole of the pick-hole type is generally provided at a manhole cover placed on a road onto which the weight of a motor vehicle is directly applied, because the other type operating hole of a larger size reduces the strength of the manhole cover to often cause the damage of the manhole cover due to the weight. In the United States, the ratio of application of a manhole cover formed with such a pick-hole type operating hole to a manhole cover amounts to 50% or more. In Japan, the pick-hole type operating hole is used for a manhole cover for a manhole for inspecting an electric cable.
Unfortunately, there was not developed a tool for efficiently lifting and transferring a manhole cover formed with such a pick-hole type operating hole. Accordingly, it was desired to develop an apparatus which is capable of effectively lifting and transferring a manhole cover having a pick-hole type operating hole while carrying out laborsaving.
The present invention is directed to an apparatus for efficiently lifting and transferring a manhole cover having pick-hole type operating holes provided opposite to each other in the diametric direction thereof wherein two lever members each having a wheel means and arranged to interpose a manhole therebetween are operated to lift the manhole, which is then transferred by means of the wheel means.
A conventional manhole operating apparatus of such type is disclosed in Japanese Utility Model Application Laid-Open Publication No. 60353/1973. The conventional apparatus is constructed in such a manner as shown in FIGS. 2A and 2B. More particularly, the manhole cover operating apparatus includes a lever body 100 comprising a pair of lever members 102 which are pivotally connected together at one end 104 thereof acting as a point of force so as to be pivotally moved with respect to each other and a wheel 106 rotatably mounted at the other end of each of the lever members 102. The apparatus also includes an operating arm 108 provided integral with each of the lever members 102 on an inside of the lever member in a manner to project in the direction opposite to that in which the lever body 100 carries out the operation of opening a manhole cover 20. Each of the operating arms 108 has a hanging hook member 112 pivotally mounted on a distal end thereof. The hanging hook member 112 is adapted to be engaged with an operating hole 22 of the manhole cover 20 to operate the manhole cover through the operating hole.
The manner of operation of the apparatus of FIG. 2 constructed as described above will be described now.
First, the hanging hook members 112 each are inserted into the operating hole 22 of the manhole cover 20 which is an operating hole defined in the British Standards and then turned by an angle of 90 degrees to engage projections provided at a lower end of the hanging hook member 112 with a lower surface of the manhole cover to support the manhole cover on the projections, so that it may be prevented from being released from the operating hole 22. Then, the one end of the lever body 100 defining the point of force 104 is pushed down to cause the lever body 100 to carry out a lever action in which the wheels 106 act as a point of support, resulting in a distal end of each of the operating arms 108 being upwardly moved. Thereafter, the manhole cover 20 held on the hanging hook members 112 is lifted and then transferred by means of the wheels 106.
However, the conventional manhole cover lifting and transferring apparatus shown in FIG. 2 has a disadvantage that it fails to securely hold a manhole cover during the operation because the hanging hook members 112 each are engaged with the manhole cover by merely abutting the projections of the hanging hook member against the lower surface of the manhole cover, so that there is a likelihood that the manhole cover is released and falls down from the apparatus due to a swing phenomenum of the manhole cover or the oscillation of the manhole cover during the lifting and transferring operation.
Also, the conventional apparatus causes the weight of the manhole cover applied to the hanging hook members 112 to generate inward moment as indicated at arrows A in FIG. 2B which acts on the whole lever body 100, resulting in the connection between the lever members 102 being substantially torsionally loaded. This requires the connection between the lever members 102 to have strength sufficient to resist such torsional load. However, this renders the provision of an operating knob means which is in parallel with operating holes of a manhole cover at the other end of the lever body highly difficult, to thereby fail to provide the apparatus with safe and efficient workability. This is exhibited especially when the operating holes are arranged away from an outer periphery of the manhole cover because such arrangement of the operating holes significantly increases the torsion moment.
Further, in the conventional manhole cover lifting and transferring apparatus, the operation of a manhole cover having operating holes provided away from an outer periphery thereof needs to arrange the hanging hook members 112 inwardly away from the wheels 106. This causes members for supporting the hanging hook members to substantially inwardly project from the lever body 100, resulting in a failure in the folding of the apparatus in a compact manner.
A still further important disadvantage encountered with the conventional apparatus is that it is applicable to a manhole cover formed with an operating hole defined in the British Standards. Accordingly, it fails to operate a manhole cover provided with the other through-hole type operating holes including a pick-hole type operating hole.